Identification and molecular typing of Streptococcus agalactiae isolated from pond-cultured tilapia in China

Bacteria strains with strong virulence were isolated from pond-cultured tilapia in China. They were identified as Streptococcus agalactiae by biochemical assays, and confirmed by 16S ribosomal RNA (rRNA) and group B Streptococcus (GBS)-specific gene cfb analyses. Multiplex polymerase chain reaction...

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Bibliographic Details
Published in:Fisheries science 2011-07, Vol.77 (4), p.623-632
Main Authors: Ye, Xing, Li, Jiong, Lu, Maixin, Deng, Guocheng, Jiang, Xiaoyan, Tian, Yuanyuan, Quan, Yingchun, Jian, Qian
Format: Article
Language:English
Subjects:
Antigens
Bacteria
Biomedical and Life Sciences
Disease prevention
Epidemiology
Fish
Fish & Wildlife Biology & Management
Fisheries
Fisheries management
Fishing
Food Science
Freshwater & Marine Ecology
Infections
Life Sciences
Morphology
Mortality
Original Article
Pathogens
Ponds
Proteins
Provinces
Streptococcus agalactiae
Streptococcus infections
Studies
Tilapia
Vaccines
Virulence
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Summary:Bacteria strains with strong virulence were isolated from pond-cultured tilapia in China. They were identified as Streptococcus agalactiae by biochemical assays, and confirmed by 16S ribosomal RNA (rRNA) and group B Streptococcus (GBS)-specific gene cfb analyses. Multiplex polymerase chain reaction (PCR) assay of the alpha C protein (ACP) gene and capsular polysaccharide antigen ( cps ) gene was employed to identify their molecular serotype (MS). Amplification of the ACP gene produced a 400-bp C alpha protein gene ( bca ) fragment, suggesting that these isolates belong to MS Ia, Ib or II; amplification of cps produced a 790-bp amplicon, indicating that they belong to MS Ia/III-3. An additional PCR based on nucleotide difference in the cps H–I region of MS Ia and III further suggested that the isolates belong to serotype MS Ia. Moreover, multi-locus sequence typing (MLST) indicated that these strains were of sequence type 7 (ST-7). These results showed that isolates from different regions of China shared the same MS and ST. However, none of the isolated ST-7 GBS corresponded to the capsular serotype, suggesting that these fish GBS possessed specific molecular characteristics not present in human or other animals. Data from this study will facilitate the understanding of epidemiology and nosogenesis of tilapia GBS and the establishment of effective disease prevention methods.
ISSN:0919-9268
1444-2906
DOI:10.1007/s12562-011-0365-4